If you somehow developed a great interest in the internetworking even though not working in that field, I'd recommand you to read THIS book to get started.
I did feel sorry that I wasted lots of time on the other 3 books I read when I started to explore internetworking. Those give me only good pieces of details about the layers, the protocols, and some parts of internetworking technology, but unclearly or loosely relate them to each other.
If you are a kind of person who's always trying to draw the big picture first with the relationships of the components among each other, and then fit in more-detailed pieces, I bet you'll be very saitisfied by this super book. You would agree that it makes sense of the parts of internetworking to the whole, and makes sense of other loosely organized books on the same topic to you, provided that you didn't ignore the importance of the first two chapters (or days' materials).
Another beauty of the book is that the details are given gradually with a very careful selection, so that you'll never get burried in the details but only controls over them. Thanks.